Hand cutters with blade guards for protection are well known and have been present in the market for many years. The need for cutting tools with the highest possible protection for the user is increasing in today's market, where many goods are shipped throughout the world. Solutions range from low cost devices with integrated blades to more sophisticated hand cutters with replaceable blades. Several means are known for providing safe handling of the cutters, both for when these are in use, as well as when they are not in use. One common solution is to stow the cutting blade within the handle of the cutting tool when it is not in use. The blade is extended out of the handle for cutting before its use and can be stowed back in the handle after its use. Another known solution is the addition of a protective guard, which can be placed over the blade, when the cutting tool is not in use.
German patent DE 3 116 354 and U.S. Pat. No. 4,086,698 show solutions with a longitudinal blade guard. This blade guard is located on the side of the cutting edge of the blade. It is permanently forced to the extended position by a spring, thus protecting the blade from accidentally cutting. This solution is designed to protect the user as soon as the blade leaves the object to be cut. However it has the disadvantage, that depending on the angle at which the blade is placed on the object, the blade guard will get jammed and must be manually pushed to the retracted position to allow cutting the object.
U.S. Pat. No. 5,697,157 shows another solution, where a guard is attached to the handle, which can be rotated between the extended position, where the blade is covered by the guard, and the retracted position, where the blade can be used for cutting. While this solution provides some protection, it does not protect from accidental use of the blade, nor does it provide protection, when the blade is being used and the user slips from the object being cut. German Patent DE 3 540 026, which has a similar type of blade guard, has an elastic mechanism permanently forcing the guard back to the extended position. It also shows a mechanism that can be used for locking the blade guard when the cutting tool is not in use. However this blade lock must be activated separately after the cutting process and again does not provide protection when the user accidentally slips from the object being cut.
Recent developments have combined the automatic protection from accidental use of the blade as shown in German Patent DE 3 116 354 and U.S. Pat. No. 4,086,698 with an automatic relocking of the blade guard as soon as the cutter is no longer in use. This is done by providing a means permanently forcing the blade guard to the position, where the user is protected, together with an automatic locking of the blade guard in the protected position, triggered by the use of the cutter. In U.S. Pat. Nos. 6,578,266 and 6,560,873 the automatic locking is triggered by a movement of the blade guard. The blade guard can be unlocked by actively pressing a button and the relocking mechanism is activated as soon as the blade guard is moved from the protected position through a contact of the blade guard with the object to be cut. The presented trigger mechanisms in these inventions require use of the thumb, which leads to a quick tiring of the user, if there are many objects that need to be cut. Also the automatic relocking can be easily triggered, when the blade guard accidentally touches the object without actually cutting it, so that it needs to be unlocked again before a cut can be made. This can lead to additional tiring of the user.